User devices, such as wireless telephones, associated with a Long Term Evolution (“LTE”) network, may wirelessly connect, or “attach,” to the network via a base station. The base station may provide multiple carriers, to which the user devices may attach. As used herein, a particular “carrier” may refer to a particular radio access technology (“RAT”), a particular frequency band, and/or a particular set of frequencies within a frequency band. A user device may attempt to connect to, or synchronize with, the network on a periodic or intermittent basis (e.g., upon an initial connection attempt, when the user device is handed over from one cell to another, when the user device is unable to connect to the network, etc.). One cell may be associated with multiple carriers. For example, in a particular coverage area, a base station may offer multiple RATs (e.g., a Third Generation Partnership Project (“3GPP”) third generation (“3G”) RAT, a 3GPP fourth generation (“4G”) RAT, etc.), multiple frequency bands (e.g., a 700 MHz frequency band, a 1700 MHz frequency band, etc.), and/or multiple intra-frequency sub-bands (e.g., an “upper” 700 MHz sub-band, a “lower” 700 MHz sub-band, etc.).
When the user device attempts to connect to the network, the network may provide a system information block (“SIB”) to the user device. The SIB may include a priority list of carriers. The user device may attempt to connect to the carrier that is highest in the priority list. If the highest priority carrier is unavailable (e.g., if the carrier is unreachable and/or does not accept the user device, such as when the carrier is overloaded), the user device may attempt to connect to the next carrier in the list, and so on.